This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The ability of humans to mount an effective immune response declines with age, leaving the elderly susceptible to infectious diseases and cancer. Moreover, vaccines tested in younger individuals are often ineffective in older people. Thus, as new vaccines are developed, it will be extremely important to test these formulations for efficacy in the elderly as well as in the young. While young nonhuman primates have been critical in testing vaccine efficacy for the general human population, a model using old nonhuman primates to assess vaccine protection for the elderly has not been established. We have begun to address this issue and in a recent study, found to our surprise that baboons, a nonhuman primate species used extensively in biomedical research, did not show immune senescence with aging. In fact, when old baboons (19-24 years old) were immunized with LcrV, a protective antigen from the plague bacterium, they responded even better than young animals (2[unreadable] years old). Thus, although age-related loss in immune function has been observed in humans, rodents and a few nonhuman primate species, baboons appear to be unusual;they age without losing immune competence. Therefore, we propose to assess the effects of aging on immunity in three nonhuman primate species (baboons, rhesus macaques, and marmosets) to multiple different antigens.